Ankylosing Spondylitis Risk Factors and Causes
The cause of ankylosing spondylitis is unknown, and the origin and development of the disease is not well understood. AS may result from a combination of genetic and environmental factors.
Ankylosing spondylitis is associated with an inherited antigen (cell marker) called HLA-B27, and more than 90 percent of patients with the disease also have this antigen. AS also is associated with inflammatory bowel diseases (IBD) such as ulcerative colitis and Crohn's disease.
Elevated levels of certain antibodies (e.g., IgA) in patients with ankylosing spondylitis, as well as the inflammatory nature of the disease, may indicate that AS is related to an immune system response.
Similarities among AS, reactive arthritis, and inflammatory bowel disease may indicate that intestinal bacteria (e.g., Klebsiella pneumoniae) play a role in disease development.